Rab27 effector Slp2-a transports the apical signaling molecule podocalyxin to the apical surface of MDCK II cells and regulates claudin-2 expression.
Rab27 effector Slp2-a transports the apical signaling molecule podocalyxin to the apical surface of MDCK II cells and regulates claudin-2 expression.
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DOI：
10.1091/mbc.e12-02-0104
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发表时间：
2012-08
影响因子：
3.3
通讯作者：
Fukuda M
中科院分区：
文献类型：
--
作者：
Yasuda T;Saegusa C;Kamakura S;Sumimoto H;Fukuda M
Slp 2-a是以Rab 27 A依赖性方式将信号分子足糖萼蛋白靶向MDCK II细胞中的顶膜所必需的。足糖萼蛋白的顶膜定位是通过调节细胞内信号（包括MAPK信号）表达紧密连接蛋白claudin-2所必需的。组织中的大多数细胞是极化的，并且通常具有两个不同的质膜结构域-顶膜和基底侧膜，这是蛋白质和脂质极化运输的结果。然而，细胞极化的机制尚未完全理解。在这项研究中，我们研究了参与突触结合蛋白样蛋白2-a（Slp 2-a），一个效应分子的小GT受体Rab 27，在极化贩运使用Madin-Darby犬肾II细胞作为模型的极化细胞。结果表明，Slp 2-a在MDCK II细胞中的表达水平随着细胞极化而大大增加，并且其表达特异性地定位于顶膜。结果还表明，Slp 2-a是以Rab 27 A依赖性方式将信号分子podocalyxin靶向顶膜所必需的。此外，足糖萼蛋白的下游靶标ezrin和ERK 1/2在Slp 2-a-敲低细胞中被激活，并且它们的激活导致紧密连接蛋白claudin-2的量急剧减少。因为Slp 2-a和密蛋白-2在小鼠肾近端小管中高度表达，所以Slp 2-a可能通过将足糖萼蛋白运输至小鼠肾小管上皮细胞中的顶端表面来调节密蛋白-2表达。
Slp2-a is required for targeting of the signaling molecule podocalyxin to the apical membrane in MDCK II cells in a Rab27A-dependent manner. Apical membrane localization of podocalyxin is required for expression of the tight junction protein claudin-2 through modulation of intracellular signals, including MAPK signals. Most cells in tissues are polarized and usually have two distinct plasma membrane domains—an apical membrane and a basolateral membrane, which are the result of polarized trafficking of proteins and lipids. However, the mechanism underlying the cell polarization is not fully understood. In this study, we investigated the involvement of synaptotagmin-like protein 2-a (Slp2-a), an effector molecule for the small GTPase Rab27, in polarized trafficking by using Madin–Darby canine kidney II cells as a model of polarized cells. The results show that the level of Slp2-a expression in MDCK II cells increases greatly as the cells become polarized and that its expression is specifically localized at the apical membrane. The results also reveal that Slp2-a is required for targeting of the signaling molecule podocalyxin to the apical membrane in a Rab27A-dependent manner. In addition, ezrin, a downstream target of podocalyxin, and ERK1/2 are activated in Slp2-a–knockdown cells, and their activation results in a dramatic reduction in the amount of the tight junction protein claudin-2. Because both Slp2-a and claudin-2 are highly expressed in mouse renal proximal tubules, Slp2-a is likely to regulate claudin-2 expression through trafficking of podocalyxin to the apical surface in mouse renal tubule epithelial cells.